History of the Prior Art
When working with various toxic and hazardous materials including radioactive samples and strong mineral acids in laboratory conditions, it is essential that care be taken to insure that such materials are safely contained so that technicians working with these materials are protected from direct exposure to the materials or any toxic vapors or airborne particles generated by the handling of said materials. When working with relatively small to moderate samples of radioactive chemicals, it has been the practice to provide a work area which is generally isolated from the surrounding environment.
The containment or isolation of hazardous and toxic laboratory chemicals is generally accomplished by providing a work area which is enclosed or covered with a hood with access to the work area being permitted only by means of small openings which allow a chemist or laboratory technician to extend their arms into the work area. As the openings into such work stations also provide an avenue by way of which hazardous materials and fumes could escape or be vented to the surrounding area, it has been the practice in the industry to provide a positive airflow through the opening and into the work area. By creating a continuous ingress of air into the covered work area, airborne contaminants are prevented from escaping therefrom.
In addition to protecting workers from the potential release of toxic substances into the ambient air, it is a secondary consideration to also protect the laboratory samples from being contaminated by particulate matter in the incoming ambient air and the air within the work station. In some prior art structures, the air within the work station is passed through filter elements before being introduced into the work area.
There are other considerations, however, which have not been adequately provided for by the work station apparatuses of the prior art. One such consideration is associated with the operation of the work station when either the ambient air supply or exhaust from the work station are interrupted. If the ambient air supply is terminated, there is no positive airflow through the access opening into the work area. Under such conditions, airborne contaminants or fumes from within the work area may escape to the surrounding environment. Likewise, if the exhaust from the work area is terminated, then it is possible that contaminates and fumes could be forced outwardly through the access opening by the air circulation means within the work station.
In addition to the foregoing, it is also necessary to provide means for removing or disposing of solids or other waste or contaminated products and articles, such as empty supply containers, tubes, tools, gloves, and the like. If such items were to be withdrawn from the controlled enclosure or work station, toxic or hazardous materials would be released to the ambient environment.
Further, if an accident or spill should occur within the work area of a controlled environment enclosure, portions of the physical structure of the work area could be severely contaminated and/or destroyed. With prior art structures, those portions of the enclosure which are most directly affected by the materials being used therein cannot be easily removed or replaced without requiring the entire work station to be dismantled.
Some examples of prior art structures for controlled work stations are disclosed in U.S. Pat. No. 3,373,323 to Whitfield; U.S. Pat. No. 3,340,788 to Landingham et al.; U.S. Pat. No. 3,811,250 to Fowler, Jr.; U.S. Pat. No. 3,895,570 to Eagleson, Jr.; U.S. Pat. No. 3,897,721 to Fuhst; and U.S. Pat. No. 4,249,463 to Hornby.